1. Field of the Invention
The present invention relates generally to grinding apparatus. More particularly, the invention concerns glass grinding apparatus, and especially table top grinders for use by hobbyists in the fabrication of glass artwork and decorative glass products.
2. Description of Prior Art
By way of background, there is a wide variety of grinding apparatus for shaping and/or surfacing many different kinds of materials. Of particular interest herein are table-top grinders of the type used by glass hobbyists and the like. Commonly assigned U.S. Pat. No. 6,416,394, entitled “Planer/Grinder For Glass,” whose contents are incorporated herein by this reference, exemplifies such equipment. The typical glass grinding apparatus includes a cylindrical grinding bit mounted on a motor-driven shaft that spins above a horizontal work piece platform. The grinding bit typically comprises a cylindrical body made of brass, aluminum or other metal that is secured to the drive shaft by way of a set screw made of steel or the like. A tubular sleeve made of nickel or other metal is mounted on the cylindrical body. The sleeve is formed with a surface coating of diamonds or other abrasive particles capable of grinding, sanding or polishing glass. A glass work piece that is to be shaped or otherwise treated is placed on the platform and advanced until its edge contacts the grinding bit. By maneuvering the work piece relative to the grinding bit, material can be selectively removed from the work piece edge to create a desired shape and/or surface treatment.
There are several problems associated with the conventional glass grinding bit described above. First, the metal body is relatively hard and when rotated at high speed may impart vibrational shock loads that can chip the glass. Second, an aqueous irrigation fluid is used to lubricate the grinding bit and cool the glass during grinding. This fluid, together with galvanic action, tends to produce corrosion between the brass set screw and the brass body such that the grinding bit may be difficult to remove after prolonged use. Third, grinding bits are offered in different grades according to the desired amount of abrasiveness (e.g., ultra-fine, fine, medium, coarse, ultra-course, etc.). Such grinding bits are sometimes difficult to differentiate because they all use the same metal body and sleeve material; only the abrasive surface is different and this difference may be difficult to detect by sight or touch.
It is to improvements in the design of glass grinding bits that the present invention is directed. In particular, what is needed is a grinding bit that overcomes one or more (and preferably all) of the above-mentioned deficiencies found in existing grinding bits.